Influence of autophagy on acute kidney injury in a murine cecal ligation and puncture sepsis model

SIRT3 MEDIATES THE CARDIOPROTECTIVE EFFECT OF THERAPEUTIC HYPOTHERMIA AFTER CARDIAC ARREST AND RESUSCITATION BY RESTORING AUTOPHAGIC FLUX VIA THE PI3K/AKT/MTOR PATHWAY

ABSTRACT

Background : Postresuscitation cardiac dysfunction is a significant contributor to early death following cardiopulmonary resuscitation (CPR). Therapeutic hypothermia (TH) mitigates myocardial dysfunction due to cardiac arrest (CA); however, the underlying mechanism remains unclear. Sirtuin 3 (Sirt3) was found to affect autophagic activity in recent research, motivating us to investigate its role in the cardioprotective effects of TH in the treatment of CA. Methods : Sprague-Dawley rats were used to establish an in vivo CA/CPR model and treated with a selective Sirt3 inhibitor or vehicle. Survival rate, myocardial function, autophagic flux, and Sirt3 expression and activity were evaluated. H9C2 cells were subjected to oxygen-glucose deprivation/reoxygenation (OGD/R) injury in vitro . The cells were transfected with Sirt3-siRNA and treated with the autophagy inhibitor chloroquine or the PI3K inhibitor LY294002, and cell viability and autophagic flux were assessed. Results : Rats exhibited decreased survival and impaired cardiac function after CA/CPR, which were alleviated by TH. Mechanistically, TH restored Sirt3 expression and autophagic flux, which were impaired by CA/CPR. Sirt3 inactivation diminished the capacity of TH to restore autophagic flux and partially abolished the improvements in myocardial function and survival. An in vitro study further showed that TH-induced restoration of disrupted autophagic flux by OGD/R was attenuated by pretreatment with Sirt3-siRNA, and this attenuation was partially rescued by the inhibition of PI3K/Akt/mTOR signaling cascades. Conclusions : Sirt3 mediates the cardioprotective effect of TH by restoring autophagic flux via the PI3K/Akt/mTOR pathway. These findings suggest the potential of Sirt3 as a therapeutic target for CA.

Restoring the infected powerhouse: Mitochondrial quality control in sepsis

Sepsis is a dysregulated host response to an infection, characterized by organ failure. The pathophysiology is complex and incompletely understood, but mitochondria appear to play a key role in the cascade of events that culminate in multiple organ failure and potentially death. In shaping immune responses, mitochondria fulfil dual roles: they not only supply energy and metabolic intermediates crucial for immune cell activation and function but also influence inflammatory and cell death pathways. Importantly, mitochondrial dysfunction has a dual impact, compromising both immune system efficiency and the metabolic stability of end organs. Dysfunctional mitochondria contribute to the development of a hyperinflammatory state and loss of cellular homeostasis, resulting in poor clinical outcomes. Already in early sepsis, signs of mitochondrial dysfunction are apparent and consequently, strategies to optimize mitochondrial function in sepsis should not only prevent the occurrence of mitochondrial dysfunction, but also cover the repair of the sustained mitochondrial damage. Here, we discuss mitochondrial quality control (mtQC) in the pathogenesis of sepsis and exemplify how mtQC could serve as therapeutic target to overcome mitochondrial dysfunction. Hence, replacing or repairing dysfunctional mitochondria may contribute to the recovery of organ function in sepsis. Mitochondrial biogenesis is a process that results in the formation of new mitochondria and is critical for maintaining a pool of healthy mitochondria. However, exacerbated biogenesis during early sepsis can result in accumulation of structurally aberrant mitochondria that fail to restore bioenergetics, produce excess reactive oxygen species (ROS) and exacerbate the disease course. Conversely, enhancing mitophagy can protect against organ damage by limiting the release of mitochondrial-derived damage-associated molecules (DAMPs). Furthermore, promoting mitophagy may facilitate the growth of healthy mitochondria by blocking the replication of damaged mitochondria and allow for post sepsis organ recovery through enabling mitophagy-coupled biogenesis. The remaining healthy mitochondria may provide an undamaged scaffold to reproduce functional mitochondria. However, the kinetics of mtQC in sepsis, specifically mitophagy, and the optimal timing for intervention remain poorly understood. This review emphasizes the importance of integrating mitophagy induction with mtQC mechanisms to prevent undesired effects associated with solely the induction of mitochondrial biogenesis.

Neutrophil elastase in dexmedetomidine alleviating sepsis-related renal injury in rats

BACKGROUND

This research was to investigate the mechanism of neutrophil elastase (NE) in dexmedetomidine (DEX) alleviates sepsis-related renal injury in rats.

METHODS

Sixty healthy male SD rats aged 6-7 weeks were randomly assigned to the control group (Sham group (S group)), Model group (M group), Model + DEX group (M + DEX group), and Model + DEX + Elaspol group (M + DEX + Elaspol (sivelestat) group), with 15 rats in each group. The renal morphology and pathological changes of different groups of rats after modeling were observed, and renal tubular injury was scored. Serum samples were collected at 6 h, 12 h, and 24 h after modeling, and the rats were sacrificed. Renal function indicators, including neutrophil gelatinase-associated lipoprotein (NGAL), kidney injury molecule-1 (KIM-1), tumor necrosis factor (TNF-α), interleukin-6 (IL-6), NE, serum creatinine (SCr), and blood urea nitrogen (BUN), were analyzed by enzyme-linked immunosorbent assay at different time periods. The level of NF-кB in renal tissue was detected by immunohistochemistry.

RESULTS

It was revealed that the general color of renal tissue in M group was dark red, swollen, and congested, and the renal tubular epithelial cells were significantly enlarged, with obvious vacuolar degeneration and inflammatory cell infiltration. Compared with M group, the color and morphology of renal tissue in M + DEX group and M + DEX + Elaspol group were improved, and the amount of inflammatory cell infiltration was reduced. The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M group were significant different from S group 12 h after the operation (P < 0.001). The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M + DEX group were significant different from M group (P < 0.01). The renal tubular injury score, SCr level, BUN level, NGAL level, KIM-1 level, TNF-α, IL-6, NE level, and NF-кB level in M + DEX + Elaspol group were significant different from those in M group at 12 h after the operation (P < 0.001).

CONCLUSION

NE plays an active role in the reduction of sepsis-related renal injury in rats by inhibiting the inflammatory response.

miR-506-3p induces autophagy of renal tubular epithelial cells in sepsis through targeting PI3K pathway

OBJECTIVE

To explore the effect of micro ribonucleic acid (miR)-506-3p on autophagy of renal tubular epithelial cells in sepsis and its mechanism.

METHODS

It was found through bioinformatics analysis that phosphatidylinositol 3-kinase catalytic subunit alpha (PIK3CA) was expressed at a low level in sepsis, and miR-506-3p had a targeted regulatory effect on PIK3CA. 40 8-week-old male C57BL/6 mice were randomly divided into control miR-506-3p NC group, control miR-506-3p OE group, sepsis miR-506-3p NC group, sepsis miR-506-3p OE group and sepsis miR-506-3p KD group. The pathological changes in kidney tissues of mice in each group were observed by hematoxylin-eosin (HE) staining and TUNEL staining, and mitochondria and autophagosomes were visualized by transmission electron microscopy. CCK8 assay was performed to detect the effect of miR-506-3p on the proliferation capacity of renal tubular epithelial cells. The changes in the expression of PI3K-Akt pathway proteins, mTOR and autophagy proteins were tested by Western blotting.

RESULTS

The injury and apoptotic positive cells were suppressed and decreased in miR-506-3p OE mice vs. NC group. miR-506-3p could increase the number of mitochondria and autophagosomes in kidney tissues. After introduction of exogenous miR-506-3p OE into renal tubular epithelial cells, the expressions of PI3K pathway proteins were significantly inhibited, while the expressions of autophagy proteins were significantly enhanced. After 740Y-P was added, the expressions of associated proteins had no significant changes in each group.

CONCLUSION

Overexpression of miR-506-3p can enhance the autophagy of renal tubular epithelial cells in sepsis through inhibiting the PI3K signaling pathway.

Epigenetic dysregulation of autophagy in sepsis-induced acute kidney injury: the underlying mechanisms for renoprotection

Sepsis-induced acute kidney injury (SI-AKI), a common critically ill, represents one of the leading causes of global death. Emerging evidence reveals autophagy as a pivotal modulator of SI-AKI. Autophagy affects the cellular processes of renal lesions, including cell death, inflammation, and immune responses. Herein, we conducted a systematic and comprehensive review on the topic of the proposed roles of autophagy in SI-AKI. Forty-one relevant studies were finally included and further summarized and analyzed. This review revealed that a majority of included studies (24/41, 58.5%) showed an elevation of the autophagy level during SI-AKI, while 22% and 19.5% of the included studies reported an inhibition and an elevation at the early stage but a declination of renal autophagy in SI-AKI, respectively. Multiple intracellular signaling molecules and pathways targeting autophagy (e.g. mTOR, non-coding RNA, Sirtuins family, mitophagy, AMPK, ROS, NF-Kb, and Parkin) involved in the process of SI-AKI, exerting multiple biological effects on the kidney. Multiple treatment modalities (e.g. small molecule inhibitors, temsirolimus, rapamycin, polydatin, ascorbate, recombinant human erythropoietin, stem cells, Procyanidin B2, and dexmedetomidine) have been found to improve renal function, which may be attributed to the elevation of the autophagy level in SI-AKI. Though the exact roles of autophagy in SI-AKI have not been well elucidated, it may be implicated in preventing SI-AKI through various molecular pathways. Targeting the autophagy-associated proteins and pathways may hint towards a new prospective in the treatment of critically ill patients with SI-AKI, but more preclinical studies are still warranted to validate this hypothesis.

Autophagy ameliorates Pseudomonas aeruginosa-infected diabetic wounds by regulating the toll-like receptor 4/myeloid differentiation factor 88 pathway

Diabetic foot ulcers (DFUs) are among the most common complications in patients with diabetes and a leading cause of lower extremity amputation. DFUs are exacerbated by prolonged bacterial infection; therefore, there is an urgent need for effective treatments to alleviate the burden associated with this condition. Although autophagy plays a unique role in pathogen phagocytosis and inflammation, its role in diabetic foot infections (DFIs) remains unclear. Pseudomonas aeruginosa (PA) is the most frequently isolated gram-negative bacterium from DFUs. Here, we evaluated the role of autophagy in ameliorating PA infection in wounds in a diabetic rat model and a bone marrow-derived macrophage (BMDM) hyperglycemia model. Both models were pretreated with or without rapamycin (RAPA) and then infected with or without PA. Pretreatment of rats with RAPA significantly enhanced PA phagocytosis, suppressed wound inflammation, reduced the M1:M2 macrophage ratio, and improved wound healing. In vitro investigation of the underlying mechanisms revealed that enhanced autophagy resulted in decreased macrophage secretion of inflammatory factors such as TNF-α, IL-6, and IL-1β but increased that of IL-10 in response to PA infection. Additionally, RAPA treatment significantly enhanced autophagy in macrophages by increasing LC3 and beclin-1 levels, which led to altered macrophage function. Furthermore, RAPA blocked the PA-induced TLR4/MyD88 pathway to regulate macrophage polarisation and inflammatory cytokine production, which was validated by RNA interference and use of the autophagy inhibitor 3-methyladenine (3-MA). These findings suggest enhancing autophagy as a novel therapeutic strategy against PA infection to ultimately improve diabetic wound healing.

The study on role of endothelial cell autophagy in rats with sepsis-induced acute kidney injury

Sepsis often causes acute kidney injury (AKI). Autophagy of renal tubular epithelial cells is considered a cytoprotective mechanism in septic AKI; however, the role of autophagy of renal endothelial cells is uninvestigated. The current study examined whether autophagy was induced by sepsis in renal endothelial cells and whether induction of autophagy in these cells attenuated the degree of AKI. Cecal ligation and puncture (CLP) was used as a model of sepsis in rats. Four experimental groups included: sham, CLP alone, CLP + rapamycin (RAPA), and CLP + dimethyl sulfoxide (DMSO), where RAPA was used as an activator of autophagy. CLP increased renal LC3-II protein levels with an additional transient increase by RAPA at 18 h. In addition, CLP induced autophagosome formation in renal endothelial cells had an additional increase induced by RAPA. Interestingly, the levels of bone morphogenetic protein and activin membrane-bound inhibitor (BAMBI), an endothelial cell-specific protein in the kidney, were also increased by CLP, albeit it was transiently downregulated by RAPA at 18 h. Serum thrombomodulin increased and renal vascular endothelial (VE)-cadherin decreased following CLP, and these changes were attenuated by RAPA. The renal cortex exhibited and inflammatory tissue damage after CLP, and RAPA alleviated these histopathological injuries. The current findings indicate that autophagy was induced by sepsis in renal endothelial cells, and upregulation of autophagy in these cells alleviated endothelial injury and AKI. In addition, BAMBI was induced by sepsis in the kidney, which may play a role in regulating endothelial stability in septic AKI.

Autophagy in acute kidney injury and maladaptive kidney repair

Acute kidney injury (AKI) is a major renal disease characterized by a sudden decrease in kidney function. After AKI, the kidney has the ability to repair, but if the initial injury is severe the repair may be incomplete or maladaptive and result in chronic kidney problems. Autophagy is a highly conserved pathway to deliver intracellular contents to lysosomes for degradation. Autophagy plays an important role in maintaining renal function and is involved in the pathogenesis of renal diseases. Autophagy is activated in various forms of AKI and acts as a defense mechanism against kidney cell injury and death. After AKI, autophagy is maintained at a relatively high level in kidney tubule cells during maladaptive kidney repair but the role of autophagy in maladaptive kidney repair has been controversial. Nonetheless, recent studies have demonstrated that autophagy may contribute to maladaptive kidney repair after AKI by inducing tubular degeneration and promoting a profibrotic phenotype in renal tubule cells. In this review, we analyze the role and regulation of autophagy in kidney injury and repair and discuss the therapeutic strategies by targeting autophagy.

Sepsis-induced AKI: From pathogenesis to therapeutic approaches

Sepsis is a heterogenous and highly complex clinical syndrome, which is caused by infectious or noninfectious factors. Acute kidney injury (AKI) is one of the most common and severe complication of sepsis, and it is associated with high mortality and poor outcomes. Recent evidence has identified that autophagy participates in the pathophysiology of sepsis-associated AKI. Despite the use of antibiotics, the mortality rate is still at an extremely high level in patients with sepsis. Besides traditional treatments, many natural products, including phytochemicals and their derivatives, are proved to exert protective effects through multiple mechanisms, such as regulation of autophagy, inhibition of inflammation, fibrosis, and apoptosis, etc. Accumulating evidence has also shown that many pharmacological inhibitors might have potential therapeutic effects in sepsis-induced AKI. Hence, understanding the pathophysiology of sepsis-induced AKI may help to develop novel therapeutics to attenuate the complications of sepsis and lower the mortality rate. This review updates the recent progress of underlying pathophysiological mechanisms of sepsis-associated AKI, focuses specifically on autophagy, and summarizes the potential therapeutic effects of phytochemicals and pharmacological inhibitors.

When a calorie isn't just a calorie: a revised look at nutrition in critically ill patients with sepsis and acute kidney injury

PURPOSE OF REVIEW

To discuss how nutritional management could be optimized to promote protective metabolism in sepsis and associated acute kidney injury.

RECENT FINDINGS

Recent evidence suggests that sepsis is a metabolically distinct critical illness and that certain metabolic alterations, such as activation of fasting metabolism, may be protective in bacterial sepsis. These findings may explain the lack of survival benefit in recent randomized controlled trials of nutrition therapy for critical illness. These trials are limited by cohort heterogeneity, combining both septic and nonseptic critical illness, and the use of inaccurate caloric estimates to determine energy requirements. These energy estimates are also unable to provide information on specific substrate preferences or the capacity for substrate utilization. As a result, high protein feeding beyond the capacity for protein synthesis could cause harm in septic patients. Excess glucose and insulin exposures suppress fatty acid oxidation, ketogenesis and autophagy, of which emerging evidence suggest are protective against sepsis associated organ damage such as acute kidney injury.

SUMMARY

Distinguishing pathogenic and protective sepsis-related metabolic changes are critical to enhancing and individualizing nutrition management for critically ill patients.

Programmed Cell Death in Sepsis Associated Acute Kidney Injury

Sepsis-associated acute kidney injury (SA-AKI) is common in patients with severe sepsis, and has a high incidence rate and high mortality rate in ICU patients. Most patients progress to AKI before drug treatment is initiated. Early studies suggest that the main mechanism of SA-AKI is that sepsis leads to vasodilation, hypotension and shock, resulting in insufficient renal blood perfusion, finally leading to renal tubular cell ischemia and necrosis. Research results in recent years have shown that programmed cell death such as apoptosis, necroptosis, pyroptosis and autophagy play important roles. In the early stage of sepsis-related AKI, autophagy bodies form and inhibit various types of programmed cell death. With the progress of disease, programmed cell death begins. Apoptosis promoter represents caspase-8-induced apoptosis and apoptosis effector represents caspase-3-induced apoptosis, however, caspase-11 and caspase-1 regulate gasdermin D-mediated pyroptosis. Caspase-8 and receptor interacting kinase 1 bodies mediate necroptosis. This review focuses on the pathophysiological mechanisms of various programmed cell death in sepsis-related AKI.

MicroRNA-103a-3p enhances sepsis-induced acute kidney injury via targeting CXCL12

Acute kidney injury (AKI) is a common and fatal complication in inflammatory sepsis. Several microRNAs (miRNAs or miRs) have been identified to control sepsis. MiR-103a-3p has been reported to take part in the various inflammatory response. However, its role in AKI remains unclear. The present research aimed to explore the role and mechanisms of miR-103a-3p in AKI. Neurogenic sepsis mouse model and lipopolysaccharide-induced HK-2 and 293 cell models were established. The renal functions in each group of mice were measured. After evaluating the biological functions of C-X-C motif chemokine 12 (CXCL12) and miR-103a-3p on HK-2 and HEK-293 T cells, their interaction was determined. Detection of CXCL12 and apoptosis and inflammation-related factors in renal tissue was done. MiR-103a-3p was significantly repressed in the sepsis model, while CXCL12 was elevated. Furthermore, miR-103a-3p inversely controlled CXCL12. Knockdown of miR-103a-3p or overexpression of CXCL12 could significantly inhibit the progression of HK-2 and HEK293 cells, whereas elevated miR-103a-3p or knockdown of CXCL12 showed the opposite effects. Collectively, miR-103a-3p heightens renal cell damage caused by sepsis by targeting CXCL12.

Pathogenesis of Multiple Organ Failure: The Impact of Systemic Damage to Plasma Membranes

Multiple organ failure (MOF) is the major cause of morbidity and mortality in intensive care patients, but the mechanisms causing this severe syndrome are still poorly understood. Inflammatory response, tissue hypoxia, immune and cellular metabolic dysregulations, and endothelial and microvascular dysfunction are the main features of MOF, but the exact mechanisms leading to MOF are still unclear. Recent progress in the membrane research suggests that cellular plasma membranes play an important role in key functions of diverse organs. Exploration of mechanisms contributing to plasma membrane damage and repair suggest that these processes can be the missing link in the development of MOF. Elevated levels of extracellular phospholipases, reactive oxygen and nitrogen species, pore-forming proteins (PFPs), and dysregulation of osmotic homeostasis occurring upon systemic inflammatory response are the major extracellular inducers of plasma membrane damage, which may simultaneously operate in different organs causing their profound dysfunction. Hypoxia activates similar processes, but they predominantly occur within the cells targeting intracellular membrane compartments and ultimately causing cell death. To combat the plasma membrane damage cells have developed several repair mechanisms, such as exocytosis, shedding, and protein-driven membrane remodeling. Analysis of knowledge on these mechanisms reveals that systemic damage to plasma membranes may be associated with potentially reversible MOF, which can be quickly recovered, if pathological stimuli are eliminated. Alternatively, it can be transformed in a non-resolving phase, if repair mechanisms are not sufficient to deal with a large damage or if the damage is extended to intracellular compartments essential for vital cellular functions.

Disruption of Kidney-Immune System Crosstalk in Sepsis with Acute Kidney Injury: Lessons Learned from Animal Models and Their Application to Human Health

In addition to being a leading cause of morbidity and mortality worldwide, sepsis is also the most common cause of acute kidney injury (AKI). When sepsis leads to the development of AKI, mortality increases dramatically. Since the cardinal feature of sepsis is a dysregulated host response to infection, a disruption of kidney-immune crosstalk is likely to be contributing to worsening prognosis in sepsis with acute kidney injury. Since immune-mediated injury to the kidney could disrupt its protein manufacturing capacity, an investigation of molecules mediating this crosstalk not only helps us understand the sepsis immune response, but also suggests that their supplementation could have a therapeutic effect. Erythropoietin, vitamin D and uromodulin are known to mediate kidney-immune crosstalk and their disrupted production could impact morbidity and mortality in sepsis with acute kidney injury.

Empagliflozin Enhances Autophagy, Mitochondrial Biogenesis, and Antioxidant Defense and Ameliorates Renal Ischemia/Reperfusion in Nondiabetic Rats

Background. Recent meta-analyses have shown that sodium-glucose cotransporter 2 (SGLT-2) inhibitors alleviate chronic kidney disease and acute kidney injury in diabetic patients. In this study, we aimed to investigate the effect of empagliflozin on renal ischemia/reperfusion (I/R) in nondiabetic rats and find the possible mechanisms. Experimental Approach. Eighteen male Wistar rats were randomly divided into three groups, including healthy control, ischemic control, and empagliflozin-treated group. Thirty minutes of bilateral renal ischemia was induced by clamping the renal hilum. Forty-eight hours after reopening the clamps, rats’ blood samples and tissue specimens were collected. Empagliflozin 10 mg/kg was administered by gavage, 2 hours before ischemia and 24 hours after the first dose. Results. I/R injury led to a significant rise in serum creatinine and blood urea nitrogen which was significantly decreased after treatment with empagliflozin. Empagliflozin also alleviated tubulointerstitial and glomerular damage and significantly decreased tissue histology scores. Empagliflozin decreased the increased levels of malondialdehyde, interleukin 1β, and tumor necrosis factor α. SGLT2 inhibition increased the decreased expression of nuclear factor erythroid 2-related factor 2 and PPARG coactivator 1 alpha that conduct antioxidant defense and mitochondrial biogenesis, respectively. Furthermore, empagliflozin markedly increased LC3-II/LC3-I and bcl2/bax ratios, showing its beneficial effect on activation of autophagy and inhibition of apoptosis. Despite its effects on diabetic nephropathy, empagliflozin did not activate the Sestrin2/AMP-activated protein kinase pathway in this study. Conclusion. Empagliflozin improved renal I/R injury in nondiabetic rats in this study by promoting autophagy and mitochondrial biogenesis and attenuation of oxidative stress, inflammation, and apoptosis.

Clinical Characteristics and Death Risk Factors of Severe Sepsis in Children

Sepsis is a systemic inflammatory response syndrome caused by viral infection. The circulatory dysfunction caused by sepsis is also called septic shock or septic shock. The main characteristics are rapid onset, rapid changes, and involvement. Multiple organs in the body make diagnosis difficult, which seriously threatens the survival of patients. As many as one million people worldwide die every year because of SIRS, it is also the leading cause of death among children in hospital ICUs. This article is aimed at studying the clinical characteristics of severe sepsis in children and the risk factors for death. Based on the analysis of the pathogenesis of sepsis and the treatment of septic shock, 65 cases of children with PICU sepsis admitted to a hospital were selected. Data, to study its clinical characteristics and risk factors for death. The results of the study showed that despite the interaction among the removal factors of the three indexes of serum lactic acid value, PCIS level, and the number of organs involved in MODS, they are still related to the mortality of children with severe sepsis.

TFEB Dependent Autophagy-Lysosomal Pathway: An Emerging Pharmacological Target in Sepsis

Sepsis is a life-threatening syndrome induced by aberrant host response towards infection. The autophagy-lysosomal pathway (ALP) plays a fundamental role in maintaining cellular homeostasis and conferring organ protection. However, this pathway is often impaired in sepsis, resulting in dysregulated host response and organ dysfunction. Transcription factor EB (TFEB) is a master modulator of the ALP. TFEB promotes both autophagy and lysosomal biogenesis via transcriptional regulation of target genes bearing the coordinated lysosomal expression and regulation (CLEAR) motif. Recently, increasing evidences have linked TFEB and the TFEB dependent ALP with pathogenetic mechanisms and therapeutic implications in sepsis. Therefore, this review describes the existed knowledge about the mechanisms of TFEB activation in regulating the ALP and the evidences of their protection against sepsis, such as immune modulation and organ protection. In addition, TFEB activators with diversified pharmacological targets are summarized, along with recent advances of their potential therapeutic applications in treating sepsis.

The effects of early restrictive fluid resuscitation on the clinical outcomes in sepsis patients

OBJECTIVE

To investigate the effects of early restrictive fluid resuscitation (RFR) on the clinical outcomes in sepsis patients.

METHODS

A total of 122 sepsis patients admitted to our hospital were recruited for this study and divided into a study group (the SG, n=56) and a control group (the CG, n=66) according to the treatment method each patient was administered. The SG was administered early RFR, and the CG was administered adequate fluid resuscitation. The clinical data were analyzed retrospectively in both groups. The total infusion volumes, the hemorrhage amounts, the urine outputs, and the Acute Physiology and Chronic Health Evaluation (APACHE II) scores were compared between the two groups. In addition, the heart rates, the mean arterial pressure levels, the central venous pressure levels, and the cardiac function indices were compared between the two groups at 1-7 days after the procedures. The survival and the complication incidence rates were followed up.

RESULTS

The SG showed significantly lower heart rates and mean arterial pressure levels and higher central venous pressure levels than the CG at 1-7 days after the procedures (P<0.05). The cardiac troponin, N-terminal brain pro-natriuretic peptide, and C-reactive protein levels at 3-7 days after the procedures in the SG were significantly lower than the levels in the CG (P<0.05). The cardiac output, stroke volume, and left ventricular ejection fraction scores in the SG were significantly higher than they were in the CG (P<0.05). The survival rate in the SG was significantly higher than it was in the CG at 16, 32, and 64 days after the procedures (P<0.05). The incidence of complications in the SG was lower than it was in the CG (P<0.05).

CONCLUSION

Early RFR can remarkably improve the clinical outcomes, the myocardial injury and survival rates, and the multiple complications incidence rate in sepsis patients.

miR‑214 ameliorates sepsis‑induced acute kidney injury via PTEN/AKT/mTOR‑regulated autophagy

Previous studies have suggested that oxidative stress and autophagy results in acute kidney injury (AKI) during sepsis and microRNA (miR)-214 serves a vital role in the protection of kidneys subjected to oxidative stress. The present study aimed to test whether the renoprotection of miR-214 is related to autophagy in sepsis. The role of autophagy was investigated in a mouse model of cecal ligation and puncture (CLP). Reverse transcription-quantitative polymerase chain reaction (RT-qPCR) was used to analyze the expression of miR-214. The structure and function of kidneys harvested from the mice were evaluated. Kidney autophagy levels were detected with immunohistochemical, immunofluorescent and western blotting. It was found that miR-214 could alleviate AKI in septic mice by inhibiting the level of kidney autophagy. Furthermore, miR-214 inhibited autophagy by silencing PTEN expression in the kidney tissues of septic mice. These findings indicated that miR-214 ameliorated CLP-induced AKI by reducing oxidative stress and inhibiting autophagy through the regulation of the PTEN/AKT/mTOR pathway.

Effect of miR-132-3p on sepsis-induced acute kidney injury in mice via regulating HAVCR1/KIM-1

OBJECTIVE

To investigate the effect of miR-132-3p and HAVCR1/kidney injury molecule (KIM)-1 on sepsis-induced acute kidney injury (AKI) in mice.

METHODS

One hundred C57BL/6 mice were divided into five groups with 20 mice in each group: the normal group (normal mice), the model group (mice with sepsis), the miR-132-3p mimic group (miR-132-3p overexpression), the oe-HAVCR1/KIM-1 group (HAVCR1/KIM-1 overexpression), and the miR-132-3p mimic + oe-HAVCR1/KIM-1 group. Dual-luciferase reporter assay was performed to verify the targeting relationship between miR-132-3p and HAVCR1/KIM-1. The expressions of miR-132-3p and HAVCR1/KIM-1 in mice' kidneys, the levels of renal function markers, the expressions of apoptosis-associated proteins, the renal cell apoptosis rate, and the inflammatory factors in serum were all examined.

RESULTS

We found that miR-132-3p can target HAVCR1/KIM-1 and regulate its expression. Compared with the normal mice, the septic mice exhibited lower miR-132-3p level and higher HAVCR1/KIM-1 level (both P<0.05). Moreover, the septic mice had higher levels of cleaved caspase-3, Bax, blood urea nitrogen, creatinine, tumor necrosis factor-α, interleukin-1β, and interleukin-6, higher renal cell apoptosis rate, and lower Bcl-2 level than the normal mice (all P<0.05). MiR-132-3p overexpression could improve the renal function of the mice with sepsis and inhibit renal cell apoptosis and inflammatory progression, whereas HAVCR1/KIM1 overexpression exhibited an opposite effect and could block the renal protective effects of miR-132-3p overexpression on the septic mice.

CONCLUSION

MiR-132-3p overexpression can inhibit renal cell apoptosis and inflammatory progression via suppressing HAVCR1/KIM-1 expression, thereby exert renal protective effects on mice with sepsis.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Mechanism of Mitophagy and Its Role in Sepsis Induced Organ Dysfunction: A Review

Autophagy, an evolutionarily conserved process, plays an important role in maintaining cellular homeostasis under physiological and pathophysiological conditions. It is widely believed that mitochondria influence the development of disease by regulating cellular metabolism. When challenged by different stimuli, mitochondria may experience morphological disorders and functional abnormalities, leading to a selective form of autophagy-mitophagy, which can clear damaged mitochondria to promote mitochondrial quality control. Sepsis is a complex global problem with multiple organ dysfunction, often accompanied by manifold mitochondrial damage. Recent studies have shown that autophagy can regulate both innate and acquired immune processes to protect against organ dysfunction in sepsis. Sepsis-induced mitochondrial dysfunction may play a pathophysiological role in the initiation and progression of sepsis-induced organ failure. Mitophagy is reported to be beneficial for sepsis by eliminating disabled mitochondria and maintaining homeostasis to protect against organ failure. In this review, we summarize the recent findings and mechanisms of mitophagy and its involvement in septic organ dysfunction as a potential therapeutic target.

Krüppel-like factor 6-mediated loss of BCAA catabolism contributes to kidney injury in mice and humans

Altered cellular metabolism in kidney proximal tubule (PT) cells plays a critical role in acute kidney injury (AKI). The transcription factor Krüppel-like factor 6 (KLF6) is rapidly and robustly induced early in the PT after AKI. We found that PT-specific Klf6 knockdown (Klf6 ^PTKD) is protective against AKI and kidney fibrosis in mice. Combined RNA and chromatin immunoprecipitation sequencing analysis demonstrated that expression of genes encoding branched-chain amino acid (BCAA) catabolic enzymes was preserved in Klf6 ^PTKD mice, with KLF6 occupying the promoter region of these genes. Conversely, inducible KLF6 overexpression suppressed expression of BCAA genes and exacerbated kidney injury and fibrosis in mice. In vitro, injured cells overexpressing KLF6 had similar decreases in BCAA catabolic gene expression and were less able to utilize BCAA. Furthermore, knockdown of BCKDHB, which encodes one subunit of the rate-limiting enzyme in BCAA catabolism, resulted in reduced ATP production, while treatment with BCAA catabolism enhancer BT2 increased metabolism. Analysis of kidney function, KLF6, and BCAA gene expression in human chronic kidney disease patients showed significant inverse correlations between KLF6 and both kidney function and BCAA expression. Thus, targeting KLF6-mediated suppression of BCAA catabolism may serve as a key therapeutic target in AKI and kidney fibrosis.

Heat shock protein 70 expression protects against sepsis-associated cardiomyopathy by inhibiting autophagy

OBJECTIVES

Increasing evidence suggests that heat shock protein 70 (Hsp70) has a protective effect in sepsis-induced cardiomyopathy; however, the protective mechanism remains unclear.

METHODS

Previous studies have also implicated autophagy in sepsis-induced cardiomyopathy. The aim of the current study was to reveal the protective mechanisms of Hsp70 in sepsis-induced cardiomyopathy using a cecal ligation and puncture (CLP) rat sepsis model. The roles of Hsp70 and autophagy in sepsis-induced cardiomyopathy were investigated by pretreating rats with the Hsp70 inhibitor quercetin or the autophagy inhibitor 3-methyladenine (3-Ma) before CLP. We also investigated the protective mechanisms of Hsp70 and the relationship between Hsp70 and autophagy in vitro by stimulating H9c2 cells with lipopolysaccharide (LPS) to simulate sepsis.

RESULTS

The result show that inhibition of Hsp70 promoted sepsis-induced death in rats, while inhibition of autophagy inhibited sepsis-induced death. These results suggested that both Hsp70 and autophagy were involved in sepsis-induced cardiomyopathy. Overexpression of Hsp70 in H9c2 myocardial cells in vitro suppressed LPS-induced apoptosis, while inhibition of autophagy with 3-Ma also decreased LPS-induced H9c2 cell apoptosis, suggesting that the protective effect of Hsp70 in sepsis-induced cardiomyopathy was related to autophagy regulation.

CONCLUSION

Overall, these results suggested that Hsp70 protected against sepsis-induced cardiac impairment by attenuating sepsis-induced autophagy.

The application of omic technologies to research in sepsis-associated acute kidney injury

Acute kidney injury (AKI) is common in critically ill children and adults, and sepsis-associated AKI (SA-AKI) is the most frequent cause of AKI in the ICU. To date, no mechanistically targeted therapeutic interventions have been identified. High-throughput "omic" technologies (e.g., genomics, proteomics, metabolomics, etc.) offer a new angle of approach to achieve this end. In this review, we provide an update on the current understanding of SA-AKI pathophysiology. Omic technologies themselves are briefly discussed to facilitate interpretation of studies using them. We next summarize the body of SA-AKI research to date that has employed omic technologies. Importantly, omic studies are helping to elucidate a pathophysiology of SA-AKI centered around cellular stress responses, metabolic changes, and dysregulation of energy production that underlie its clinical features. Finally, we propose opportunities for future research using clinically relevant animal models, integrating multiple omic technologies and ultimately progressing to translational human studies focusing therapeutic strategies on targeted disease mechanisms.

Polydatin Alleviates Septic Myocardial Injury by Promoting SIRT6-Mediated Autophagy

Sepsis is a life-threatening condition. Polydatin (PD), a small natural compound from Polygonum cuspidatum, possesses antioxidant and anti-inflammatory properties. However, the protective mechanism of PD on sepsis-induced acute myocardial damage is still unclear. The aim of this study was to investigate the effect and mechanism of action of PD on lipopolysaccharide (LPS)-induced H9c2 cells and in a rat model of sepsis, and explored the role of PD-upregulated sirtuin (SIRT)6. LPS-induced H9c2 cells were used to simulate sepsis. Cecal ligation and puncture (CLP)-induced sepsis in rats were used to verify the protective effect of PD. ELISA, western blotting, immunofluorescence, immunohistochemistry, and flow cytometry were used to study the protective mechanism of PD against septic myocardial injury. PD pretreatment suppressed LPS-induced H9c2 cell apoptosis by promotion of SIRT6-mediated autophagy. Downregulation of SIRT6 or inhibition of autophagy reversed the protective effect of PD on LPS-induced apoptosis. PD pretreatment also suppressed LPS-induced inflammatory factor expression. CLP-induced sepsis in rats showed that PD pretreatment decreased CLP-induced myocardial apoptosis and serum tumor necrosis factor-α, interleukin (IL)-1β, and IL-6 expression. 3-Methyladenine (autophagy inhibitor) pretreatment prevented the protective effect of PD on septic cardiomyopathy. SIRT6 expression was increased with PD treatment, which confirmed that PD attenuates septic cardiomyopathy by promotion of SIRT6-mediated autophagy. All these results indicate that PD has potential therapeutic effects that alleviate septic myocardial injury by promotion of SIRT6-mediated autophagy.

GSTP1 Inhibits LPS-Induced Inflammatory Response Through Regulating Autophagy in THP-1 Cells

Glutathione S-transferase Pi (GSTP1) was originally identified as one of the cytosolic phase II detoxification enzymes and was also considered to function via its non-catalytic, ligand-binding activity. Autophagy is a self-protective mechanism of the cell to remove unnecessary or dysfunctional components, which plays a crucial role in balancing the beneficial and detrimental effects of immunity and inflammation. However, little is known about whether and how GSTP1 mediates autophagy via inhibiting LPS-induced inflammatory response. Here, we show that LPS-induced autophagy and autophagic flux blockade in THP-1 cells in a concentration- and time-dependent manner. Further, we found that the autophagy activation inhibited the activation of inflammatory signaling pathway and the release of inflammatory factors. However, inhibition of autophagy by 3-methyladenine or chloroquine significantly reduced the anti-inflammatory effect of GSTP1. In addition, our findings provide evidence that GSTP1 regulates autophagy through PI3K-Akt-mTOR pathway and inhibits LPS-induced inflammation. Overall, the current study provides an important reference for future applications of GSTP1 in the treatment of inflammatory diseases.

Interplay Between NLRP3 Inflammasome and Autophagy

The NLRP3 inflammasome is cytosolic multi-protein complex that induces inflammation and pyroptotic cell death in response to both pathogen (PAMPs) and endogenous activators (DAMPs). Recognition of PAMPs or DAMPs leads to formation of the inflammasome complex, which results in activation of caspase-1, followed by cleavage and release of pro-inflammatory cytokines. Excessive activation of NLRP3 inflammasome can contribute to development of inflammatory diseases and cancer. Autophagy is vital intracellular process for recycling and removal of damaged proteins and organelles, as well as destruction of intracellular pathogens. Cytosolic components are sequestered in a double-membrane vesicle-autophagosome, which then fuses with lysosome resulting in degradation of the cargo. The autophagy dysfunction can lead to diseases with hyperinflammation and excessive activation of NLRP3 inflammasome and thus acts as a major regulator of inflammasomes. Autophagic removal of NLRP3 inflammasome activators, such as intracellular DAMPs, NLRP3 inflammasome components, and cytokines can reduce inflammasome activation and inflammatory response. Likewise, inflammasome signaling pathways can regulate autophagic process necessary for balance between required host defense inflammatory response and prevention of excessive and detrimental inflammation. Autophagy has a protective role in some inflammatory diseases associated with NLRP3 inflammasome, including gouty arthritis, familial Mediterranean fever (FMF), and sepsis. Understanding the interregulation between these two essential biological processes is necessary to comprehend the biological mechanisms and designing possible treatments for multiple inflammatory diseases.

Long noncoding RNA HOXA-AS2 mediates microRNA-106b-5p to repress sepsis-engendered acute kidney injury

HOXA cluster antisense RNA 2 (HOXA-AS2) is a long noncoding RNA associated with the development of numerous cancers. But, whether HOXA-AS2 exhibits a certain function in sepsis-engendered acute kidney injury (AKI) remains uninvestigated. We strived to unveil the role of HOXA-AS2 in sepsis-engendered AKI. The expression of HOXA-AS2 in sepsis patients, animal models and lipopolysaccharide (LPS)-impaired HK-2 cells was primarily assessed via a real-time quantitative polymerase chain reaction. The effects of HOXA-AS2 on cell survival of HK-2 cells under LPS irritation were evaluated after overexpression of HOXA-AS2. The correlation between HOXA-AS2 and microRNA (miR)-106b-5p was forecasted via bioinformatics software and verified by using a luciferase report system. Subsequently, the functions of miR-106b-5p in LPS-damaged HK-2 cells were reassessed. Western blot was used for the determination of Wnt/β-catenin and nuclear factor-κB (NF-κB) pathways. HOXA-AS2 expression was decreased in sepsis patients, animal operation group and LPS-irritated HK-2 cells. Overexpressed HOXA-AS2 mollified LPS-triggered impairment in HK-2 cells. In addition, a negative mediatory relation between HOXA-AS2 and miR-106b-5p was predicated. Synchronously, overexpressed miR-106b-5p counteracted the protection of HOXA-AS2 in LPS-damaged HK-2 cells. Ultimately, Wnt/β-catenin and NF-κB pathways were hindered by HOXA-AS2 via targeting miR-106b-5p. HOXA-AS2 exhibited protection in sepsis-engendered AKI via targeting miR-106b-5p and hindering the Wnt/β-catenin and NF-κB pathways.

Autophagy in kidney disease: Advances and therapeutic potential

Autophagy is a highly conserved intracellular catabolic process for the degradation of cytoplasmic components that has recently gained increasing attention for its importance in kidney diseases. It is indispensable for the maintenance of kidney homeostasis both in physiological and pathological conditions. Investigations utilizing various kidney cell-specific conditional autophagy-related gene knockouts have facilitated the advancement in understanding of the role of autophagy in the kidney. Recent findings are raising the possibility that defective autophagy exerts a critical role in different pathological conditions of the kidney. An emerging body of evidence reveals that autophagy exhibits cytoprotective functions in both glomerular and tubular compartments of the kidney, suggesting the upregulation of autophagy as an attractive therapeutic strategy. However, there is also accumulating evidence that autophagy could be deleterious, which presents a formidable challenge in developing therapeutic strategies targeting autophagy. Here, we review the recent advances in research on the role of autophagy during different pathological conditions, including acute kidney injury (AKI), focusing on sepsis, ischemia-reperfusion injury, cisplatin, and heavy metal-induced AKI. We also discuss the role of autophagy in chronic kidney disease (CKD) focusing on the pathogenesis of tubulointerstitial fibrosis, podocytopathies including focal segmental glomerulosclerosis, diabetic nephropathy, IgA nephropathy, membranous nephropathy, HIV-associated nephropathy, and polycystic kidney disease.

Autophagy in Kidney Disease

Autophagy is a cellular homeostatic program for the turnover of cellular organelles and proteins, in which double-membraned vesicles (autophagosomes) sequester cytoplasmic cargos, which are subsequently delivered to the lysosome for degradation. Emerging evidence implicates autophagy as an important modulator of human disease. Macroautophagy and selective autophagy (e.g., mitophagy, aggrephagy) can influence cellular processes, including cell death, inflammation, and immune responses, and thereby exert both adaptive and maladaptive roles in disease pathogenesis. Autophagy has been implicated in acute kidney injury, which can arise in response to nephrotoxins, sepsis, and ischemia/reperfusion, and in chronic kidney diseases. The latter includes comorbidities of diabetes and recent evidence for chronic obstructive pulmonary disease-associated kidney injury. Roles of autophagy in polycystic kidney disease and kidney cancer have also been described. Targeting the autophagy pathway may have therapeutic benefit in the treatment of kidney disorders.

The Role of Autophagy in Sepsis: Protection and Injury to Organs

Sepsis is a systemic inflammatory disease with infection, and autophagy has been shown to play an important role in sepsis. This review summarizes the main regulatory mechanisms of autophagy in sepsis and its latest research. Recent studies have shown that autophagy can regulate innate immune processes and acquired immune processes, and the regulation of autophagy in different immune cells is different. Mitophagy can select damaged mitochondria and remove it to deal with oxidative stress damage. The process of mitophagy is regulated by other factors. Non-coding RNA is also an important factor in the regulation of autophagy. In addition, more and more studies in recent years have shown that autophagy plays different roles in different organs. It tends to be protective in the lungs, heart, kidneys, and brain, and tends to be damaging in skeletal muscle. We also mentioned that some drugs can regulate autophagy. The process of modulating autophagy through drug intervention appears to be a new potential hope for the treatment of sepsis.

Autophagy flux in critical illness, a translational approach

Recent clinical trials suggest that early nutritional support might block the induction of autophagy in critically ill patients leading to the development of organ failure. However, the regulation of autophagy, especially by nutrients, in critical illness is largely unclear. The autophagy flux (AF) in relation to critical illness and nutrition was investigated by using an in vitro model of human primary myotubes incubated with serum from critically ill patients (ICU). AF was calculated as the difference of p62 expression in the presence and absence of chloroquine (50 µM, 6 h), in primary myotubes incubated for 24 h with serum from healthy volunteers (n = 10) and ICU patients (n = 93). We observed 3 different phenotypes in AF, non-altered (ICU non-responder group), increased (ICU inducer group) or blocked (ICU blocker group). This block was not associate with a change in amino acids serum levels and was located at the accumulation of autophagosomes. The increase in the AF was associated with lower serum levels of non-essential amino acids. Thus, early nutrition during critical illness might not block autophagy but could attenuate the beneficial effect of starvation on reactivation of the autophagy process. This could be of clinical importance in the individual patients in whom this process is inhibited by the critical illness insult.

Protective role of thymoquinone in sepsis-induced liver injury in BALB/c mice

Sepsis increases the risk of developing liver injury. Previous studies have demonstrated that thymoquinone (TQ) exhibits hepatoprotective properties in vivo as well as in vitro. The present study aimed to investigate the underlying mechanisms of the protective effects of TQ against liver injury in septic BALB/c mice. Male BALB/c mice (age, 8 weeks) were randomly divided into four groups, namely, the control, TQ (50 mg/kg/day) treatment, cecal ligation and puncture (CLP), and TQ + CLP groups. CLP was performed following gavage of TQ for 2 weeks. At 48 h post-CLP, the histopathological alterations in the liver tissue (LT) and plasma levels of serum alanine aminotransferase (ALT), aspartate aminotransferase (AST) and alkaline phosphatase (ALP) were assessed. The present study evaluated microtubule-associated protein light chain 3 (LC3), sequestosome-1 (p62) and beclin 1 protein expression by western blotting and immunostaining, as well as interleukin (IL)-6, IL-1β, IL-10, monocyte chemoattractant protein-1 (MCP-1) and tumor necrosis factor-α (TNF-α) mRNA expression by RT-qPCR. The results of the present study indicated that administration of TQ to mice reduced the histological alterations caused by CLP in LT. TQ inhibited the plasma levels of ALT, AST and ALP in the CLP group. TQ significantly inhibited the elevation of p62, IL-1β, IL-6, MCP-1 and TNF-α levels as well as increased the LC3, beclin 1 and IL-10 levels in LT. PI3K expression in the TQ + CLP group was significantly decreased compared with that in the CLP group. TQ treatment effectively modulated the expression levels of p62, LC3, beclin 1, PI3K and proinflammatory cytokines, and may be an important agent for the treatment of sepsis-induced liver injury.

PPARα contributes to protection against metabolic and inflammatory derangements associated with acute kidney injury in experimental sepsis

Sepsis-associated acute kidney injury (AKI) is a significant problem in critically ill children and adults resulting in increased morbidity and mortality. Fundamental mechanisms contributing to sepsis-associated AKI are poorly understood. Previous research has demonstrated that peroxisome proliferator-activated receptor α (PPARα) expression is associated with reduced organ system failure in sepsis. Using an experimental model of polymicrobial sepsis, we demonstrate that mice deficient in PPARα have worse kidney function, which is likely related to reduced fatty acid oxidation and increased inflammation. Ultrastructural evaluation with electron microscopy reveals that the proximal convoluted tubule is specifically injured in septic PPARα deficient mice. In this experimental group, serum metabolomic analysis reveals unanticipated metabolic derangements in tryptophan-kynurenine-NAD+ and pantothenate pathways. We also show that a subgroup of children with sepsis whose genome-wide expression profiles are characterized by repression of the PPARα signaling pathway has increased incidence of severe AKI. These findings point toward interesting associations between sepsis-associated AKI and PPARα-driven fatty acid metabolism that merit further investigation.

The protective role of autophagy in sepsis

Sepsis is characterized by life-threatening organ dysfunction caused by a deregulated host response to infection. Autophagy is one of the innate immune defense mechanisms against microbial attack. Previous studies have demonstrated that autophagy is activated initially in sepsis, followed by a subsequent phase of impairment. A number of sepsis-related studies have shown that autophagy plays a protective role in multiple organ injuries partly by clearing pathogens, regulating inflammation and metabolism, inhibiting apoptosis and suppressing immune reactions. In this review, we present a general overview of and recent advances in the role of autophagy in sepsis and consider the therapeutic potential of autophagy activators in treating sepsis.

Mitochondrial quality control mechanisms as potential therapeutic targets in sepsis-induced multiple organ failure

Sepsis is a dysregulated response to severe infection characterized by life-threatening organ failure and is the leading cause of mortality worldwide. Multiple organ failure is the central characteristic of sepsis and is associated with poor outcome of septic patients. Ultrastructural damage to the mitochondria and mitochondrial dysfunction are reported in sepsis. Mitochondrial dysfunction with subsequent ATP deficiency, excessive reactive oxygen species (ROS) release, and cytochrome c release are all considered to contribute to organ failure. Consistent mitochondrial dysfunction leads to reduced mitochondrial quality control capacity, which eliminates dysfunctional and superfluous mitochondria to maintain mitochondrial homeostasis. Mitochondrial quality is controlled through a series of processes including mitochondrial biogenesis, mitochondrial dynamics, mitophagy, and transport processes. Several studies have indicated that multiple organ failure is ameliorated by restoring mitochondrial quality control mechanisms and is further amplified by defective quality control mechanisms. This review will focus on advances concerning potential mechanisms in regulating mitochondrial quality control and impacts of mitochondrial quality control on the progression of sepsis.

Role of C-reactive protein in the pathogenesis of acute kidney injury

Acute kidney injury (AKI) is characterized by both non-inflammatory and inflammatory process, and accumulating evidence has demonstrated that inflammation plays a key role in the pathogenesis and progression of AKI. C-reactive protein (CRP), an acute reactant produced by liver and many inflammatory cells, acts not only as an inflammation biomarker, but also as a pathogenic factor for AKI. Indeed, increased concentration of CRP is associated with poor outcome of varied etiologically related AKI patients. In recent years, the role of CRP is gradually recognized as an active participant in the pathogenesis and progression of AKI by exacerbating local inflammation, impairing the proliferation of damaged tubular epithelial cells and promoting fibrosis of injured renal tissue.

Potential therapy strategy: targeting mitochondrial dysfunction in sepsis

Recently, the definition of sepsis was concluded to be a life-threatening organ dysfunction caused by a dysregulated host response to infection. Severe patients always present with uncorrectable hypotension or hyperlactacidemia, which is defined as septic shock. The new definition emphasizes dysregulation of the host response and multiple organ dysfunction, which is partially attributed to metabolic disorders induced by energy crisis and oxidative stress. Mitochondria are a cellular organelle that are well known as the center of energy production, and mitochondrial damage or dysfunction is commonly induced in septic settings and is a predominant factor leading to a worse prognosis. In the present review, we determine the major mitochondrial disorders from morphology to functions in sepsis. In the following, several clinical or pre-clinical assays for monitoring mitochondrial function are demonstrated according to accumulated evidence, which is the first step of specific therapy targeting to modulate mitochondrial function. Accordingly, various reagents used for regulating mitochondrial enzyme activities and promoting biogenesis have been documented, among which mitochondria-targeted cation, TPP-conjugated antioxidants are the most valuable for future trials and clinical treatment to improve mitochondrial function as they may take advantage of the prognosis associated with septic complications.